A RARE CASE OF CARPAL MELORHEOSTOSIS
ABSTRACT
Melorheostosis is a rare, non-inheritable sclerotic bone dysplasia. We report a rare case of
melorheostosis involving the carpal bones of a 9 years old male who presented with pain in
right wrist joint on palmar flexion. Plain radiograph and CT performed revealed
characteristic appearance of melorheostosis involving the scaphoid, lunate and trapezium.
CASE REPORT
A 9 Years old male child presented with complaints of persistent pain in right wrist joint over
1 month with limitation palmar flexion of the wrist.
On physical examination the terminal extenet of palmar and dorsi flexion of the right wrist
joint were restricted. Grip strength of right wrist is maintained. There was no significant
limitation of daily activities.
Plain radiographs revealed hyperostosis of the scaphoid,lunate and trapezium involving both
the cortex and medulla. There was no significant periosteal reaction. The carpal joint spaces
were maintained. No obvious erosions / lytic lesions were noted.
Computed tomography (CT) scans showed a high attenuation involving cortical hyperostosis.
Biochemical analysis including serum calcium, phosphorus, alkaline phosphatase, C-reactive
protein and erythrocyte sedimentation rate revealed no significant abnormality.
A core biopsy was taken form the scaphoid and histopathological analysis revealed
nonspecific, dense cortical bone replacing the trabacular system.
DISCUSSION:
Melorheostosis is a rare non hereditary sclerosing bone dysplasia first described by the two
French neurologists Leri and Joanny in 1922 (1).
The origin of the word melorheostosis is from a combination of the Greek words ‘melo’
meaning 'limb', ‘rheos’ meaning 'flow' and ‘osteon’ meaning 'bone' (2). This was in reference
to the classic appearance on plain radiographs where the sclerosis appears to flow along the
long axis of the bone, akin to candle wax dripping down one side of a candle.
Pathologically, this condition comprises of new bone formation on the periosteal and
endosteal layers of the diaphyseal cortical bone. Typically, this is seen as irregular sclerosis
olong one side of a long bone. This condition most often affects the long bones of both the
upper and lower extremities but may rarely affect small bones of the hands and feet or even
the axial skeleton (3). Within the hand, the short long bones like phalanges and metacarpals
are usually involved and isolated involvement of the carpal bones is very rare.
The exact cause of this condition is yet unknown. However, several theories have been
proposed including a genetic mutation involving the LEMD3 gene , an embryonal
mesodermal disorder, a vascular abnormaltiy and even infection of associated nerve roots (4).
The last theory was probably proposed to explain the common occurrence of this disorder in
particular sclerotomes.
Several patterns of melorheostosis have been described including the monostotic (involving
one bone), polysototic (involving multiple bones) and the most common monomelic
(involving one limb). Within a limb, melorheostosis is usually confined to a single sclerotome
and even within a particular sclerotome, the lesions may cross the joint space to involve
bones on either side but the intervening joint is usually not involved (5).
Melorheostosis is often associated with various cutaneous manifestations overlying the
involved bones including focal scleroderma, neurofibromatosis, various vascular and
lymphatic malformations including telengiectasias. These skin changes usualllly parallel the
bone involvement and are often restricted to the involved sclerotome (6).
Clinically, melorheostosis is a chronic disorder with slow progression of symptoms. The
usual presentation is with pain, joint stiffness, muscle contracture, limitation of motion, soft
tissue abnormalities or progressive deformity (7). It has no sex prediliction and over 50% of
the patients are diagnosed before the age of 20 years (8).
The diagnosis of melorheostosis is usually based on classical imaging findings alone and a
biopsy is usally not required. Also, histopathological analysis is most often not diagnostic.
On plain radiographs, there is increased bone density and the hyperostosis is classically
present along the cortical aspect of one side of bone resembling flowing candle wax – the
'dripping candle wax' sign (9). In carpal and tarsal bones and in the epiphysis of long bones,
the hyperostosis maybe round or irregular, as in our case. The CT appearance is similar to the
typical undulating hyperostosis seen on radiographs (10). These lesions appear well
demarcated from the normal bone. On MR examination, sclerosis appears of low in signal
intensity on both T1 and T2 wighted images. CT and MRI further help in delineating the soft
tissue changes.
The radiological differential disgnoses include osteopoikilosis, osteopetrosis, arthrogryposis
multiplex congenita, and osteopathia striata (11). Radionuclide bone scan maybe useful in
differentiating melorheostosis from its mimics by demonstrating increased radiotracer uptake
in the involved bones on blood pool as well as delayed phases in this condition (12). When it
affects the carpal bones, as in our case, the differential diagnosis would broaden to include
other causes of carpal boen sclerosis including kienbock's disease, rhematoid arthritis,
chronic infections like tuberculosis, etc and often histopathology maybe required to rule out
these conditions.
Melorheostosis is a benign condition and usually does not need treatment. However,
bisphosphonates have been reported to provide significant symptomatic relief by decreasing
the bone turnover (13).
CONCLUSION
Although melorheostosis is a relatively easy diagnosis to make radiologically when it
involves long bones, it maybe very difficult to diagnose involevement of small bones of the
hands and feet. It is very important for radiologists and clinicians to be aware of this
condition and its radiological appearance so as to maek an early diagnosis and avoid
unecessary intervention.
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FIGURE LEGEND: CT Scan of right wrist joint of 9 year old male child showing
hyperostosis of the scaphoid, lunate and trapezium. A – Scout (AP), B – VRT, C – CT
sagittal, D – CT axial and E – CT coronal.